1. Field of the Invention
The present invention relates generally to a tape carrier in which wiring patterns are formed on an insulating base film, and a method of manufacturing such a tape carrier. More particularly, the present invention relates to a tapes carrier with high density wiring patterns which is bent easily and which has a high reliability, and a method of manufacturing such a tape carrier. The present invention also relates to a tape carrier package (TCP) which is fabricated by attaching a semiconductor chip on such tape carrier, and a liquid crystal display device having such a TCP.
2. Description of the Related Art
A tape carrier package (TCP) used in a liquid crystal display and the like is often used in condition it is bent or folded at predetermined portion or portions thereof. Conventionally, TCP""s having various structures are used to obtain good bending characteristics such as easiness of bending and the like.
For example, there is known a tape carrier structure disclosed in Japanese patent laid-open publication No. 7-28866. FIG. 4 is a cross sectional view showing schematically the tape carrier structure disclosed in Japanese patent laid-open publication No. 7-28866. The tape carrier shown in FIG. 4 comprises an insulating base film 31, and a wiring pattern portion 35 bonded to the insulating base film 31 with glue 34. On the wiring pattern portion 35, there is formed a solder resist layer or film 37. Also, a device hole 32 for mounting a semiconductor device is formed in the base film 31. Further, slits 33 are formed in the base film 31 along bending portions thereof. By forming such slits 33, it becomes possible to easily bend the tape carrier 38 along the slits 33. Further, in order to protect the wiring pattern portion 35 exposed via the slits 33, and to avoid disconnection or break of the wiring pattern portion 35, a protective resin film 36 made of polyimide and the like is formed on portions of the wiring pattern portion 35 exposed via the slits 33.
There is also known a tape carrier structure disclosed in Japanese patent laid-open publication No. 8-306741. FIG. 5 is a cross sectional view showing schematically the tape carrier structure disclosed in Japanese patent laid-open publication No. 8-306741. The tape carrier of FIG. 5 comprises an insulating base film 41 made of flexible and soft material, and a wiring pattern portion 44 bonded on the base film 41 with glue 43. A surface of the wiring pattern portion 44 opposite to the base film 41 is coated with a solder resist layer 48. Also, in the base film 41, a device hole 42 is formed for mounting a semiconductor device. In this structure, no slit is formed in the base film 41 to facilitate bending of the base film 41. However, a film for reinforcement 45 which is somewhat rigid and which has a slit 47 is bonded onto the base film 41 with glue 46 on the surface opposite to the wiring pattern portion 44. Thereby, the tape carrier 49 can be easily foldable along the slit 47.
However, in the structure described in Japanese patent laid-open publication No. 7-28866 and shown in FIG. 4, it is necessary to apply the protective resin film 36 of polyimide onto the portions of the wiring pattern portion 35 exposed via the slit 33. Therefore, process steps for manufacturing such a tape carrier become complicated, and throughput of manufacturing is also deteriorated.
In the structure described in Japanese patent laid-open publication No. 8-306741 and shown in FIG. 5, it is necessary to use the film 45 for reinforcement in addition to the base film 41. Thus, it needs many kinds of materials used for fabricating such tape carrier, and it results in increase of the cost.
Further, in the tape carrier structure disclosed in Japanese patent laid-open publication No. 4-342148, wiring patterns made of copper (Cu) foil which is plated with tin (Sn) are formed on an upper surface of a base film which is a plastic film made of polyimide, polyester or the like. In a bending region of the base film, slit shaped openings for bending are formed by wet etching. The slit shaped openings are parallel with the wiring patterns respectively and are formed between adjacent wiring patterns such that wiring patterns are not exposed via the slit shaped openings. Each of the slit shaped openings has a width of 60 xcexcm (micrometers) and a length of 4 mm, and has a tapered cross section which becomes wider toward the bottom side of the base film at an angle of 30-60 degrees. The slit shaped openings are formed at a pitch of 200 xcexcm.
In the tape carrier described in Japanese patent laid-open publication No. 4-342148, elongated slit shaped openings are formed parallel with the wiring patterns and formed between the wiring patterns throughout the bending area. Therefore, when the tape carrier is bent or a stress is applied to the tape carrier from the outside, the stress is concentrated at portions near end portions of the slit shaped openings so that there is a possibility that the base film is damaged. In order to avoid such disadvantage, it is necessary to increase the thickness of the base film to enhance the strength thereof. However, when the thickness of the base film is increased, it becomes difficult to bend the tape carrier, and it results in increase of weight and the cost of the tape carrier.
In Japanese patent laid-open publication No. 4-342148, another structure of a tape carrier is disclosed in which many and small round openings are formed by wet etching in a bending area of a base film on which wiring patterns are formed. Each of the round openings is formed between the wiring patterns such that the wiring patterns are not exposed via the round openings.
However, in this structure, since the round openings are formed between adjacent wiring patterns, when respective spaces between adjacent wiring patterns are small, it is difficult to form appropriately the round openings in the base film such that sufficient flexibility of the base film is obtained. Therefore, it is not appropriate to use this structure when spaces between wiring patterns are small. Recently, it is required that wiring patterns are formed in high density on a base film of a tape carrier, so that spaces between the wiring patterns on the base film must be very small. Thus, this structure does not suit such recent tape carrier in which wiring patterns are formed in high density.
Also, in this structure, since small round openings are formed between respective wiring patterns, it is impossible to enlarge the proportion of areas of openings in the bending area of the tape carrier sufficiently. Therefore, it is impossible to obtain good bending characteristics, such as sufficient flexibility at desired portion or portions of a tape carrier.
Therefore, it is an object of the present invention to obviate the above-mentioned disadvantages of the prior art.
It is another object of the present invention to provide: a tape carrier which has a simple structure, improved bending characteristics and high mechanical strength; a method of manufacturing such a tape carrier; a TCP using such a tape carrier; and a liquid crystal display device comprising such a TCP.
It is still another object of the present invention to provide: a tape carrier which can be bent easily and appropriately at a desired bending region; a method of manufacturing such a tape carrier; a TCP using such a tape carrier; and a liquid crystal display device comprising such a TCP.
It is still another object of the present invention to provide: a tape carrier which can be manufactured at low cost and which can be bent easily and appropriately at a desired bending region; a method of manufacturing such a tape carrier; a TCP using such a tape carrier; and a liquid crystal display device comprising such a TCP.
It is still another object of the present invention to provide at low cost: a tape carrier which can be bent easily and appropriately at a desired bending region without deteriorating the mechanical strength; a method of manufacturing such a tape carrier; a TCP using such a tape carrier; and a liquid crystal display device comprising such a TCP.
It is still another object of the present invention to provide at low cost: a tape carrier in which wiring patterns can be formed at high density on a base film and which can be bent easily and appropriately at a desired bending region; a method of manufacturing such a tape carrier; a TCP using such a tape carrier; and a liquid crystal display device comprising such a TCP.
According to an aspect of the present invention, there is provided a tape carrier comprising: a base film made of an insulating material; wiring patterns formed on the base film; and a bending area of the base film in which a plurality of holes are formed regularly, the width of each of the holes in the direction perpendicular to the wiring patterns being larger than a space between the wiring patterns in the bending area.
In this case, it is preferable that each of the plurality of holes has a round shape.
It is also preferable that the holes are formed such that the centers of the holes are located at grid points of an assumed grid structure which is composed of lines parallel with the wiring patterns and lines perpendicular to the wiring patterns and at the intersections of diagonal lines connecting the grid points.
It is further preferable that the distance between adjacent grid points is four times a pitch of the wiring patterns in the bending area.
It is advantageous that the center of each of the plurality of holes is located on the center line of a space between adjacent wiring patterns in the bending area.
According to another aspect of the present invention, there is provided a tape carrier package comprising: a base film made of an insulating material; wiring patterns formed on the base film; one or more semiconductor device each mounted on or in a device hole formed at the base film; and a bending area of the base film in which a plurality of holes are formed regularly, the width of each of the holes in the direction perpendicular to the wiring patterns being larger than a space between the wiring patterns in the bending area.
In this case, it is preferable that each of the plurality of holes has a round shape.
It is also preferable that the holes are formed such that the centers of the holes are located at grid points of an assumed grid structure which is composed of lines parallel with the wiring patterns and lines perpendicular to the wiring patterns and at the intersections of diagonal lines connecting the grid points.
It is further preferable that the distance between adjacent grid points is four times a pitch of the wiring patterns in the bending area.
It is advantageous that the center of each of the plurality of holes is located on the center line of a space between adjacent wiring patterns in the bending area.
According to still another aspect of the present invention, there is provided a liquid crystal display device which comprises a tape carrier package as mentioned above.
According to still another aspect of the present invention, there is provided a method of manufacturing a tape carrier, the method comprising: preparing a base film made of an insulating material; forming a plurality of holes regularly in a bending area of the base film; and forming wiring patterns on a surface of the base film; wherein the width of each of the holes in the direction perpendicular to the wiring patterns being larger than a space between the wiring patterns in the bending area.
In this case, it is preferable that the method of manufacturing a tape carrier further comprises: forming sprocket holes and at least one device holes each for mounting a semiconductor device therein or thereon in the base film.
It is also preferable that the forming a plurality of holes regularly in a bending area of the base film and the forming sprocket holes and at least one device holes each for mounting a semiconductor device therein or thereon in the base film are performed in substantially the same process step.
It is further preferable that, in the forming a plurality of holes regularly in a bending area of the base film, the holes are formed by punching which uses metallic die.
It is advantageous that, in the forming a plurality of holes regularly in a bending area of the base film, the holes are formed by etching.
It is also advantageous that each of the plurality of holes has a round shape.
It is further advantageous that the holes are formed such that the centers of the holes are located at grid points of an assumed grid structure which is composed of lines parallel with the wiring patterns and lines perpendicular to the wiring patterns and at the intersections of diagonal lines connecting the grid points.
It is preferable that the distance between adjacent grid points is four times a pitch of the wiring patterns in the bending area.
It is also preferable that the center of each of the plurality of holes is located on the center line of a space between adjacent wiring patterns in the bending area.